Magnetically operated, multi-position, pressure control valve having integral metering orifice

ABSTRACT

The present invention relates to a pressure control valve including a valve tappet which is axially movably arranged in the valve housing and, in a first switch position, provides a pressure fluid connection between a first pressure fluid port that opens into the valve housing and a second pressure fluid port that opens into the valve housing, wherein the valve tappet, in a second switch position, separates the pressure fluid connection between the first pressure fluid port and the second pressure fluid port and, in a third switch position, provides a pressure fluid connection between the second pressure fluid port and a third pressure fluid port, to which end a valve closure member which is axially slidable by the valve tappet is lifted from its valve seat. Another valve closure member is arranged in the valve housing so as to be displaceable in relation to the valve tappet, the valve closure member providing an unimpeded pressure fluid connection between the first pressure fluid port and the second pressure fluid port in a first operating position of the valve tappet and interrupting the pressure fluid connection between the first and the second pressure fluid port in another operating position, and, in the first operating position, having a valve opening cross-section which constantly adjusts the pressure fluid volume flow between the first and the second pressure fluid port.

BACKGROUND OF THE INVENTION

The present invention relates to a pressure control valve, in particularan electrically operable multi-way valve for hydraulic automotivevehicle brake systems with wheel slip control.

German patent No. 29 09 504 discloses a pressure control valve whereinthe valve tappet is configured as a slide valve for pressure control inorder to provide a pressure fluid connection between a first and asecond pressure fluid port in a first switch position and to separatethe above-mentioned pressure fluid ports in a second switch position ofthe valve slide. In the third switch position, the valve tappet willopen a spherical non-return valve, thereby opening another pressurefluid connection to the second pressure fluid port.

However, a shortcoming of the pressure control valve is that the valveslide, on the one hand, necessitates a high degree of fitting precisionto be able to govern leakage flows at the control edge which areresponsive to manufacture and temperature. On the other hand, noprovision is made to ensure the pressure reduction in the connected linesystem in case the valve slide becomes jammed.

European patent No. 0 353 635 discloses a valve assembly having a slidevalve which acts as a flow control valve. The flow control valvegenerally has a piston which controls the volume flow between a pressurefluid source and a pressure fluid consumer as a function of the switchposition of an electromagnetically operated actuating member. To performthis function, the piston has a relatively long stem with through-boreswhich include control edges. The control edges cover the pressure fluidchannels of the pressure fluid consumer or the pressure fluid sourcewhich open radially into the valve housing. Undesired leakage due to theannular slot in the area of the control edge cannot be prevented inspite of the relatively long piston stem. Further, the serialarrangement of the flow control valve and the electromagneticallyoperable actuating member causes a substantial structural volume of thevalve assembly. Sealing problems which are typical of slide valves willoccur.

OBJECT OF THE INVENTION

Therefore, an object of the present invention is to provide a pressurecontrol valve which ensures a functionally reliable pressure control anda compact and miniaturized structure by simple means. In particular, thepressure fluid supply shall be achieved by using a seat valve and afluid volume which is as independent as possible of the tandem mastercylinder pressure, thereby contributing to minimizing valve switchingnoises. In addition, the valve shall permit a pressure-maintain phaseand generally include a quick-reaction operation at low response forces.

SUMMARY OF THE INVENTION

According to the present invention, this object is achieved by thecharacterizing features of patent claim 1, wherein another valve closuremember is arranged in the valve housing so as to be displaceable inrelation to the valve tappet. The valve closure member provides anunimpeded pressure fluid connection between the first pressure fluidport and the second pressure fluid port in a first operating positionand interrupts the pressure fluid connection between the first and thesecond pressure fluid port in another operating position. In the firstoperating position, the valve closure member has a metering orifice at abore step with a valve opening cross-section which controls the pressurefluid volume flow between the first and the second pressure fluid port.

Further objects, features, advantages and possible applications of thepresent invention can be seen in the following description of anembodiment.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a pressure control valve, in a longitudinal cross-sectionalview which is enlarged several times.

DETAILED DESCRIPTION OF THE DRAWING

A valve housing 1 of the pressure control valve, having a cartridgedesign, is retained in a valve block in a caulked manner. A deepdrawnvalve sleeve 11 is retained in the valve housing 1 made of steel by acaulked portion provided in the end area of the valve sleeve 11. Toattach the valve housing 1 and the valve sleeve 11, further attachmentmethods involving positive engagement and/or operative engagement areappropriate which are, however, not dealt with in this embodiment. Thedome area of the valve sleeve 11 accommodates the magnetic armature 12on which valve tappet 2 is mounted. Valve tappet 2 extends through abore of the magnetic core 13 up to a pressure chamber 14. The base ofthe valve sleeve 11 staked with the valve housing 1 is supported on themagnetic core 13. Valve sleeve 11 accommodates a valve coil 15 whichensures the electromagnetic actuation of the valve tappet 2. Thepressure chamber 14, which is disposed downstream of the magnetic core13, accommodates an annular piston 7 which is axially movable andmetallically sealed within the pressure chamber 14.

The portion of the annular piston 7 close to the magnetic core 13 has anannular groove 16 which includes a pressure fluid passage between afirst pressure fluid port 5 and a bore step 10 of the pressure chamber14 adjacent to the magnetic core 13. The bore step 10 can be closed by aportion on the annular piston 7 which is enlarged and forms the secondvalve closure member 3. The second valve closure member 3, in theconstruction of a seat valve member which extends like a ball externallyto the annular groove 16, is a component part of the annular piston 7.The end surface of the annular piston 8 remote from the valve closuremember 3 extends up to the area of a second pressure fluid port 8 whichalso opens radially into the pressure chamber 14. In the disclosedembodiment, the second pressure fluid port 8 provides the wheel brakeport for a hydraulic brake system with wheel slip control. On the otherhand, the first pressure fluid port 5 is connected to the port of abraking pressure generator 25. A third pressure fluid port 17 which isclosed by a valve closure member 18 in the direction of the pressurechamber 14, as shown, is connected to a pressure fluid collecting means26 which stores the pressure fluid originating from the wheel brake portand redelivers it to the first pressure fluid port 5 in case of need.Both valve closure members 3, 18 which act as seat valves are arrangeddiametrally relative to each other and are operable independently ofeach other, oppositely in terms of their effect. The valve closuremember 18, which is arranged upstream of the third pressure fluid port17, can be cracked open by electromagnetic actuation of the valve tappet2 exclusively in opposition to a compression spring 9 which acts uponthe valve closure member 18 in the closing direction. The second valveclosure member 3 mounted on the annular piston 7 can perform a closingmovement, by way of the valve tappet 2 and by biassing of a compressionspring 8. The closing movement is initiated by a compression spring 28arranged above the annular piston 7. The valve tappet 2 extendscoaxially in relation to the two oppositely acting compression springs8, 28 up to the valve closure member 18 which is arranged downstream ofthe pressure fluid port 6. The valve tappet 2 includes a step 4 withinthe annular piston 7. On step 4, a disc 31 having a metering orifice 23is supported and urged against a step 21 in the annular piston 7 underthe action of the compression spring 8. The disc 31 can also be designedintegrally by the valve tappet 2, and the metering orifice may beconfigured as a notch, recess, flattened portion or any similarly shapedprovision on the valve tappet, on the one hand, and by the step 21, onthe other hand. The annular piston 7 functions as a volume flow controlvalve on which the valve closure member 3, which is open in the initialposition, is mounted as an integral component. Undesirable leakage flowsbetween the first and the second pressure fluid port 5, 6 are minimized,preferably by a slot sealing with pressure relief grooves on theperiphery of the annular piston 7. The annular grooves (pressure reliefgrooves) on the periphery of the annular piston 7 prevent a one-sidedcontact with the bore wall. The valve housing 1 (valve cartridge) issealed in the valve accommodating block by self-caulking and annularsealing. Ring and plate filters 19, 20 keep the interior of the pressurecontrol valve clean.

The operation of the pressure control valve in connection with ahydraulic automotive vehicle brake system with wheel slip control willbe explained hereinbelow.

The drawing shows the pressure control valve in the electromagneticallynon-energized switch position which, simultaneously, refers to the brakerelease position and the normal braking phase when the valve is used fora slip-controlled brake system. In this position, there is an unimpededpressure fluid connection from the braking pressure generator 25 throughthe first pressure fluid port 5, the annular filter element 19, theannular groove 16, the open valve closure member 3 and the openingcross-section of the metering orifice 23 in the annular piston 7 in thedirection of the second pressure fluid port 6 which ends at the wheelbrake 24. Starting from a minimum volume flow Qmin, a constant pressuredifference results at the metering orifice 23 and determines the volumeflow.

As shown in the drawing, the valve tappet 2 is remote from the valveclosure member 18 which, under the action of the compression spring 9,separates the pressure fluid connection between the first and secondpressure fluid ports 5, 6 and the pressure fluid port 17 which leads tothe pressure fluid collecting means 26.

When inadmissibly high wheel slip values occur which are detected bysuitable means of a signal evaluating electronic unit when the vehicleis overbraked, the coil 15 is electromagnetically energized, with theresult that the magnetic armature 12 performs a stroke movement. Duringthe stroke movement, the compression spring 8 is compressed by way ofthe disc-shaped stop on the step 4 of the valve tappet 2 so thatcompression spring 28, which abuts on the end surface of the annularpiston 7 above the compression spring 8, moves the valve closure member3 towards the bore step 10 for closing. In a binary switching operationof the valve, the valve tappet 2 lifts the valve closure member 18, inopposition to the effect of the compression spring 9, from its valveseat in the valve housing 1. This causes the pressure fluid compressedbetween the pressure chamber 14 and the wheel brake 24 to flow throughthe second orifice 30, which is arranged downstream of the valve closuremember 18, in the direction of the pressure fluid collecting means 26.The magnetic armature 12 is in abutment on the magnetic core 13, or ananti-adhesive washer is interposed. Calibration of the orifice 30determines the pressure reduction gradient. When an analog control isused to actuate the valve tappet 2, a pressure-maintain phase can beadjusted in contrast to the binary operation of the valve tappet 2. Thepressure-maintain phase is achieved by an intermediate position of thevalve tappet stroke where the upper valve closure member 3 has just beenclosed and the lower valve closure member 18, which is closed in theinitial position, is not yet actuated by the valve tappet 2. A volumeflow control by way of the annular groove 16 is performed in dependenceon the size of the metering orifice 23 in the direction of the wheelbrake 24. When the magnetic armature 12 is in its maximum strokeposition, the valve closure member 18 which is cracked open by the valvetappet 2, will exclusively perform pressure control so that the orifice30, following the valve closure member 18 that is closed in the initialposition, is not required in the event of analog operation of themagnetic armature 12. Thus, the pressure in the wheel brake 24 can bedischarged very quickly in the direction of the pressure fluidcollecting means 26. A pump 27 supplies the pressure fluid escaping fromthe wheel brake 24 to the braking pressure generator 25 or the pressurecontrol valve.

If oversteering of the electrohydraulic pressure modulation, to theeffect of a pressure reduction initiated manually by way of the brakingpressure generator 25 (brake pedal moves to the release position), isneeded during the pressure-maintain phase or pressure increase phase,the pressure in the wheel brake 24 can be reduced at any time in thedirection of the first pressure fluid port 5 by way of a non-return cupseal 22 fitted on the valve housing 1.

If pressure shall be re-increased in the wheel brake 24 upon completionof the pressure reduction phase, the electromagnetic energization of themagnetic armature 12 will be interrupted, with the result that theannular piston 7, under the effect of the compression spring 8, moves inthe direction of the magnetic core 13 to adopt its initial positionagain. The pressure fluid which originates from the braking pressuregenerator 25 and is applied to the annular groove 16 is again conductedthrough the passage at the valve closure member 3, in dependence on apressure difference which is adjusted constantly on the metering orifice23, and with a constant volume flow. The annular piston 7 moves to abreathering position which governs the opening cross-section on the borestep 10. In the breathering position, the resilient force resulting fromthe two compression springs 8, 28, as a function of the cross-sectionalsurface of the annular piston 7, is in balance with the pressuredifference adjusted on the metering orifice 9. In the present case ofapplication for an anti-lock brake system, the above described flowcontrol function acts above a defined response pressure of a few bar.The advantage of the flow control function is that a constant pressureincrease gradient is achieved irrespective of pressure variationsbetween the braking pressure generator 25 and the wheel brake 24. Thepressure increase gradient can be maintained irrespective of therespective pilot pressure of the braking pressure generator 25 which isabove the response pressure of the flow control valve. This avoidsnoises which previously occurred due to differently sized pressurepulses during the braking pressure control phase. The presentarrangement of the annular piston 7, acting as a flow control valve,permits maintaining a valve closure member 3, which is open in theinitial position, and maintaining a valve closure member 18 which issuitable for the pressure reduction phase and is also configured as aseat valve. A particularly compact pressure control valve is therebyachieved which combines the advantages of seat valves which areelectromagnetically open and closed in their de-energized state with theadvantage that a volume flow control function is ensured which, inparticular, causes low noise and is simple and reliable. Further,possible leakages are excluded almost completely. The employment of ananalog valve operation is particularly favorable and permits thepreviously known flow control function in two-way/two-positiondirectional control valves for use in three-way/three-positiondirectional control valves with a pressure-balanced seat valve member.Because the function of the valve closure member 3 is almost independentof the differential pressure between the braking pressure generator 25and the wheel brake 24, a pressure control valve having a particularlyquick switching operation is achieved so that smaller valve coils 15with a lower energy consumption may be used. Further, the proposedpressure control between the second and the third pressure fluid port 6,17 permits simplifying the electronics because no additional electricactuators are required for the actuation of the valve closure member 18which acts as a spherical non-return valve.

We claim:
 1. A pressure control valve including a valve tappet which isaxially movably arranged in the valve housing and, in a first switchposition, provides a pressure fluid connection between a first pressurefluid port that opens into the valve housing and a second pressure fluidport that opens into the valve housing, wherein the valve tappet, in asecond switch position, separates the pressure fluid connection betweenthe first pressure fluid port and the second pressure fluid port and, ina third switch position, provides a pressure fluid connection betweenthe second pressure fluid port and a third pressure fluid port to whichend a first valve closure member, which is axially slidable by the valvetappet, is lifted from its valve seat,wherein a second valve closuremember is arranged in the valve housing so as to be displaceable inrelation to the valve tappet, the second valve closure member providingan unimpeded pressure fluid connection between the first pressure fluidport and the second pressure fluid port in a first switch position ofthe valve tappet and interrupting the pressure fluid connection betweenthe first and the second pressure fluid port in another switch position,and, in the first switch position, the second valve closure memberhaving a metering orifice at a bore step with a valve openingcross-section which adjusts the pressure fluid volume flow between thefirst and the second pressure fluid port wherein the second valveclosure member includes a transition area, tapering as an annulargroove, to the annular piston which provides an unimpeded hydraulicconnection between the first pressure fluid port and the pressurechamber.
 2. The pressure control valve as claimed in claim 1, whereinthe second valve closure member is configured as a seat valve alignedcoaxially to the valve tappet.
 3. The pressure control valve as claimedin claim 1, wherein the second valve closure member is fitted to anannular piston which is sealed and axially movable in a pressurechamber.
 4. The pressure control device as claimed in claim 3, whereinthe annular piston has a metering orifice which bears against steps ofthe valve tappet and the annular piston.
 5. The pressure control deviceas claimed in claim 3, wherein the annular piston on either end is actedupon by compression springs which are supported on end surfaces thatconfine the pressure chamber.
 6. The pressure control valve as claimedin claim 5, wherein the valve tappet extends coaxially to thecompression springs and through the annular piston until ahead of one ofthe valve closure members.
 7. The pressure control device as claimed inclaim 5, wherein, in the electromagnetically non-energized position ofthe magnetic armature, the compression spring moves the annular pistonalong with the valve tappet into a switch position where a pressurefluid connection between the pressure fluid port and the second pressurefluid port is provided.
 8. A pressure control valve including a valvetappet which is axially movably arranged in the valve housing and, in afirst switch position, provides a pressure fluid connection between afirst pressure fluid port that opens into the valve housing and a secondpressure fluid port that opens into the valve housing, wherein the valvetappet, in a second switch position, separates the pressure fluidconnection between the first pressure fluid port and the second pressurefluid port and, in a third switch position, provides a pressure fluidconnection between the second pressure fluid port and a third pressurefluid port to which end a first valve closure member, which is axiallyslidable by the valve tappet, is lifted from its valve seat,wherein asecond valve closure member is arranged in the valve housing so as to bedisplaceable in relation to the valve tappet, the second valve closuremember providing an unimpeded pressure fluid connection between thefirst pressure fluid port and the second pressure fluid port in a firstswitch position of the valve tappet and interrupting the pressure fluidconnection between the first and the second pressure fluid port inanother switch position, and, in the first switch position, the secondvalve closure member having a metering orifice at a bore step with avalve opening cross-section which adjusts the pressure fluid volume flowbetween the first and the second pressure fluid port wherein the annularpiston on either end is acted upon by compression springs which aresupported on end surfaces that confine the pressure chamber wherein, inthe electromagnetically non-energized position of the magnetic armature,the compression spring moves the annular piston along with the valvetappet into a switch position where a pressure fluid connection betweenthe pressure fluid port and the second pressure fluid port is provided.